I went and actually bought the tool from Mini/BMW. $150
Friggen Highway robbery considering they tried to tell me I would have to come to the dealer everytime I wanted the brake pads changed. I told them I wasn't playing that game and there were laws preventing them from doing exactly that. Guess that's why they screwdrivered me with the price.
Anyway, found outthis is the same tool once used on the BMW 3 series and can be found in some autoparts stores. System has a long screw which attaches to a small cylinder with 4 nubs to fit the indentations in the caliper piston. further up on the bolt is a piece that looks somewhat like a brake pad that slides into place on the caliper. This provides pressure as your screwing the caliper piston in. Be careful not to go too far in as you can tear the rubber boot on the piston.